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Full text of "The Cambridge Natural History"

124

MARSUPIAL " LARVAE "

are the precise equivalents of similar bones in the Monotremata.
It has been held, but apparently erroneously, that these bones
are mere ossifications in the tendons of the external oblique
muscle of the abdomen, or of the pyramidalis of the same region;
and vestiges have been asserted to exist in the Dog. Such
bonelets are undoubtedly present in the
Dog; but it seems clear from their develop-
ment in Marsupials, as structures actually
continuous with the median unossified por-
tion of the symphysis pubis, that the
" marsupial bones" belong to that part of
the skeleton, and that they correspond with
the epipubis of certain amphibians and
reptiles. The pouch, it may be remarked,
exists in a rudimentary form in the males
of many Marsupials.

The most salient feature in the life-
history of the Marsupials is the imperfect
condition in which the young are born.
The egg is no longer
laid, as in the Mono-
trenies; but curiously

FIQ. 60.Ventral surface of   enough       the      OVUIll,

innominate bone of Kan-   whlch   has   the

garoo (Jtfatropwi mayor).

x J.   , Acetabulum ; &,   Size    of    that    of    the

supiai" bone; j&, pubic  completely     at     the
i'#SS5S^  first division (as Mr.

supra-iliac   border ;   **,   Caldwell  has   shown),
sacral surface: thf, thy-        ,        , , .         T        ,

roid  foramen;  tf, tuber-   ail(i       fclllf3       develop-

osity of ischium.   <From  mental   feature   may

Flower's Osteology.)                   ,                         i     i     i

perhaps     be     looked

upon as a reminiscence of a former large-
yolked condition. The young when born
are small and wide; the newly bom young of a large Kangaroo
is perhaps as large as the little finger- The young are trans-
ferred by the lips of the mother to the pouch, where they are
placed upon a teat. It is an interesting fact that they are
not merely imperfect foetuses, but that they are actual larvae.
They possess in fact at any rate one larval organ in the shape of

O. 61,-Mammary foetus
of Kangaroo attached to
the teat, (Nat. size.)
(From Parker awl Hns-
weU'fl Zoology-)